Secondary batteries are highly applicable to a wide range of products and have electrical characteristics with high energy density. Such secondary batteries are applied not only to portable electronic devices but also to electric vehicles, hybrid vehicles, and electric power storage devices, driven by electric driving sources.
A battery pack applied to an electric vehicle and the like is configured so that a plurality of battery modules, each having a plurality of battery cells, are connected to obtain a high output. Each battery cell may be repeatedly charged and discharged by an electrochemical reaction among components including a positive electrode current collector, a negative electrode current collector, a separator, an active material, an electrolyte and the like.
Meanwhile, along with an increased need for a large capacity structure and utilization as energy storage sources in recent years, there is a growing demand for a multi-module battery pack in which a plurality of battery modules, each having a plurality of secondary batteries connected in series or in parallel, are aggregated.
Meanwhile, if conventional circular secondary batteries are applied in the battery module, when the battery cells are coupled, electrode terminals of the battery cells are welded to bus bars, respectively. In addition, in order to protect the circular secondary batteries, protection plates are separately provided to upper and lower portions of the battery module.
However, in the above configuration of the battery module, bus bars coupled by welding when the battery cells are electrically coupled are separately provided, which results in a complex structure and a complicated battery module manufacturing process. Also, since the bus bars should be provided separately, the material cost is increased.